Light-projection apparatus.



0. E. CONKLIN & H. P. HOLLNAGEL.

LIGHT PROJECTION AFPARATUS.

APLlcATloN FILED MAY1 2. |911.

Patenfd Apr. 1,1919.

@HIVER ELE C0 maar raton.

l ElILIN, 0F BOSTON, AND HERBERT PERCIVL HOLLNGEL, OF WEST NEWTON,IVIASSCHUSETTS.

LIGHT-PROJECTION' AAPP r.

his invention relates to the production of a concentrated' beam of light and more particularly to an automobile headlight or a military searchlight 'adapted to produce a ilat beam of light whose spread is adapted to illuminate any desired horizontal are in a given plane without projecting much if any light obliquely to the plane, this applin cation being in the nature of an improvement on our. prior application Sr. No. 129,001, filedNovember 1, 1916.4

The principal objects .of the invention are to project a concentrated beam of light horiinvention is tov produce a beam of light zontally without wasting light upwardly or downwardly, thereby to obtain a moreperfect control or the beam, to provide improved projecting apparatus having a focal region of at least one substantial dimension whereby a relatively large light source may be employed and still be maintained in the focus of the.l

reflector so as to reduce a concentrated beam of light. nother object or the of such angular extent in the horizontal direction as .to avoid the necess ty of sweeping the searchlight over the harizon in order to illuminate a considerable area, as for example, 1n illuminating a broad expanse of water. Still another vobject of the invention is to provide projection apparatus of such character 'that an incandescent lamp canl be used for `producing high power beams, thus .avoiding the necessity of using arc lamps for the purpose. p. Other objects of the invention will b`e apparent from the following description andthe accompanying drawings, which are largely diagrammatic, in which,

Figure 1 is a vertical longitudinal central section of one embodiment of the invention; Fig. 2 is a horizontal longitudinal central section of the same embodiment, taken on line 2-'2 of Fig. 1;

Specication of` Letters Patent.

Patenten npr. i, rara..

Application :tiled May 12, 1917. Serial No, ll'?.

`Fig. 3 i's a vertical longitudinal central. section of another embodiment of the invention;

Fig. 4 is a horizontal lon itudinal central section of the second embo iment taken on line 4-4 of Fig. 3; y

Fig. 5 is al diagram in perspective illus trating the operation of the apparatus;

Fig. Gis a diagram in side elevation corresponding to Fig. 5; j

Fig. 7 is a view in horizontal central section of the diagrams in Figs. 5 and 6;

Fig. 8 is a view similar to that of Fig. 7, showing the conjoint use or reecting and reiracting light deflecting means in combination with a cylindrical reflector; and

Fig. 9 is a horizontal section of a modilied form of refracting means.

The present invention involves apparatus for producing a beam of light, the vertical spread of which is made suiliciently smallto avoid the useless projection of light above and below the horizontal plane, and which is therefore adapted to increase the concentration of light along the horizontal. By virtue of the peculiar construction of the apparatus the lateral spread of the beam can be determined independently of the vertical spread. This peculiar construction consists primarily in the use of separate means for controlling the lateral and vertical spread of the beam, and in the embodiment of the invention shown in Figs. 1 and 2 this construction is as follows:

A main reflector M havinga substantially cylindrical contour, that is, a contour generated by the movement of a substantially straight line remaining parallel to itself and constantly intersecting a curve, is disposed, for the preferred uses of the invention, with its axial plane substantially horizontal. For most purposes the cylindrical reilector is given a parabolic contour as shown in Fig. 1, although it is to be understood that other contours such as the cliptical or hyperboloidal or other contour may be employed instead ofthe parabolic. The

parabolic reector M, instead of having a the axis of the reector M in the central region of the focal region FF. r1`he cylindrical bulb B may be mounted in any convenient manner, but for the purpose of illustration we have shown it mounted in openings 1 in the end walls E of the reflectors, gaskets or washers 2 preferably being provided between the lamp bulb and the annular edges of the end Walls E surrounding the lamp bulb. l I

For a purpose hereinafter described, the end'walls E are preferably made reflecting on their inner surfaces and they are preferably given a contour similar to that of the main reflector M, that is, a parabolic cylindrical contour. 'Andin the preferred construction of the apparatus shown in Figs. 1 and 2, the focal line of the parabolic end walls E is disposed substantially coincident with the directrix D of the central element of the main parabolic reflector M, it being understood that the directrix lD is disposed in the rear cf the reflector a distance equal to the focal length of the reflector and in perpendicular relationship to the horizontal axial plane of the reflector. If the end walls E were continued around the rear of the main reflector M theywould be disposed along the dash line E shown in Fig. 2 and would meet in the rear of the-directrix D of the main reflector M, as indicated.

The embodiment of the invention'shown in Figs. 3 and 4-is similar to that shown in Fig. 1, but instead of having parabolic end walls E the end Walls may be given any suitable contour, flat end walls as shown at E1 being suitable. Over the front of the parabolic cylindrical reflector R is placed a lens C which is cylindrical and which has its line focus disposed at the rear of the reflector R, and preferably substantially coincident with the directrix D1 of the reflector R. As shown in Figs. 3 'and 4, the spherical lamp bulb B1 may be employed instead of acylindrical lamp bulbr as in Figs. 1 and 2, and it is to be understood that either type of bulb may be employed in either embodi' ment of the invention. As in Figs. 1 and 2, the light source L, in Figs. 3 and 4 is preferably rectilinear and preferably disposed along the line focus F1 of the reflector R.

The operation of both types of the improved apparatus will be more clear by reference to the diagrams in Figs. 5 to 7. 1n these diagrams a parabolic cylindrical redector P is shown in outline, this reflector correspondingvto the main reflectors M and R in Figs. 1 to 4. lThe parabolic reflector P has a line focus F2 and its vertical longitudinal central section has a directrix D2. A ray of light a emanating from the central point 3 of the line focus F2 and striking the reflector F at 4 will be reflected horizontally as shown in Fig. 6, but in a horizontal direction` oblique to the central vertical plane of the reflector which contains thepoint 3 and the vdirectrix D2, the particular iparabolic element of the reflector P which Figs. 5 to 7, each of the reflected rays of light which'radiate from point 3 to the reflector, illustrated for example by rays a and b, are reflected by reflector P as if coming from the directrix D2. Thus, if lines be extended rearwardly in the direction of the reflected rays they will intersect the directrix. In Figs. 5 and 6 for example, the reflected rays a and if continued rearwardly would intersect the directrix D2 at points a and b respectively. This is true of all rays emanating from the central point of the li'ne focus F2 and forms the basis of the present invention. l

By disposing arabolic end reflecting walls as shown in 4igs. 1 and 2 all rays of light such as rays 7,8, t, u and e, which emanate from the central po-int of the line focus F and which are reflected from the main reflector M to the end walls E, will be projected in parallelism to the axis of the reflector, this resulting from the fact that the main reflector M renders the rays para-llel to the horizontal axial plane of the apparatus and the end walls E render the rays parallel to the vert-ical axial plane of the apparatus. This is due tothe fact that, as described in connection with Figs. 5 to 7, all such `rays are reflected from the main reflector as if coming from the directrix D of the main reflector, and inasmuch as the line focus of the end Walls E is coincident with the direc'trix, rays directed from the directrix are likewise directed from the focus of the end wallsv and will therefore be rendered parallel to the axial plane containing the directrix D. A ray t, for example, striking the main reflector M at 7 will be reflected as if coming from the point 8 in the directrix D to the end reflector E at point 9, the ray thence being projected in fparallel relationship to the axis 10 of the re ector. Likewise the rays u and fv striking the main reflector at points 11 and 12 respectively will be reflected to the points 13 and 14 of the end walls along paths which if extended rearwardly will intersect the directrix at points 15 and 16, and thence be projected in arallelism with the axis 10.

ig. 2 only s ows rays striking the lower half of the reflector, but rays striking the upper half of the reflector, such as rays r and s in Fig. 1, would be projected in like manner.

In the embodiment of the invention shown in Figs. 3 and 4 similar resultsvare obtained but in a slightly different manner. In t h1s embodiment all vrays of light emanatmg from the central point 17 of the light source and striking the reflector R will, as above explained, be refiected as if coming from the direetrix D1, a virtual image of the light source being formed along the directrix. Inasmuch as the focus ofthe cylindrical lens C is coincident with the directrix D1, the rays reflected from reflector R,.wh1ch appear to come from the virtual image of the light source at the focus of' the cylindrical lens -are rendered parallel to the vertical axial plane of the apparatus. The reflector R renders the rays rparallel to the horizontal axial plane as above described, and consequently the rays are rendered parallel to the axis 20 of the apparatus. To make this clear, rays o andp have been .shown as emanating from the' central point 17 to the points 21 and 22 of the reflector R, the `rays thence being' reflected along "lines intersecting the directrix at points 23 and 24 to the cylindrical lens C, where they are rendered parallel tothe axis 20. Rays such as m and n striking the upper half of the reflector would be refiected 1n like manner as if coming from points 25 and 26 in thedirectrix D1. When employing the cylindrical lens C the end walls E1 may be either light reflecting, light di'using or light absorbing, but they are preferabl so constructed as, to

diffuse the light inci ent thereto, the dif-` fused light passing outwardly through the y cylindrical lens so as to illuminate objects l the `forward end outside of the main beam of. light relatively feebly.

From the above description it will be apparent that the essential characteristics of the present invention involve two optical means, one of which renders the rays substantially parallel to a horizontal` plane and the other of which renders the rays substantially parallel to a vertical plane. Another characteristic feature involves the use of optical means, one or more ,of which have line foci, one of the foci being disposed in the region of the virtual focus of the other means. While these characteristics may be utilized in any one of a number of embodiments, two of the embodiments being shown means for most purposes is that shown in ll `igs. 3 and 4. It will be understood that the'width of the apparatus. may be varied suitably to determine the proportionate amounts of light reflected'from the end walls and passing directly through the opening in of the apparatus respectively. In the embodiment in Figs. 1 and 2, for example, by making the width relatively small the ratio of light incident directly to the end walls to the amount of light rst striking the main reflector can b e increased, and vice versa. In the embodlment shown in Figs. 3 and 4 the ratio of the light reflected directly through the lens C to the diffused light from the end walls E1 may be increased by increasing the width of the main reflector and cylindricall lens.

It will also be understood that a certain amount of lateral flare will result when employing a light source extending along the line focus of the main reflector on either side of the central point of the line focus, and by varying the length of the light source the lateral spread of the beam may be controlled. By increasing the length of the l light is reflected upwardly or downwardly, a

fan-shaped beam being produced on the contrary, the lateral spread of which can be controlled as above described. When employing apparatus for automobile headlighting Where it is desirable to prevent light being projected upwardly but to project some light downwardly to the nearer and 100 y intermediate portions of the roadway any Well-known means may be employed to direct a portion of the light downwardly. For

example, either the upper or lower half of the reflector may be given a different contour or a different position with respect to the light source than the other half.'

While the use of parabolic -end walls and a. cylindrical lens have been described sepa rately, it is to be understood'that they may be employed conjointly if desired, and indeed the best results are obtained by using the two features conjointly. This may be done, for example, as shown in Fig. 8, whereln a main reliector 31 is provided with parabolic end walls 32 and 33 having their foci coincident with the directrix 3lof the central parabolic element of the parabolic cylindrical reflector 31. A cylindrical lens 36 is positioned in front of the main reflector 31 in the same manner as described in connection with Figs. 3 and 4f except that .the lens only extends across the central portion of the front of the reflector, leaving spaces 37 and 38 on either side of the lens between the lens and the end walls 32 and 33. With this arrangement all rays of light,

issuing from the central point 39 of the focus of the main reflector 31 which are reflected from the main reector 31 directly to the cylindrical lens, as are rays 41 and 42, will 1 direction as the rays 41 and 42, that is, in a direction parallel to the vertical central plane of the main reflector 31, which plane contains the directrix 34, it being understood that all of these rays are rendered parallel to the central horizontal plane containing the axis of the main reflector 31 by the main lreflector 31. With the combined arrangement shown in Fig. 8 both the rays which are reeclted Yfrom the main reflector to the end reflectors and those rays which.

are reflected bythe main reflector through the cylindrical reflector 36 are rendered parallel to the vertical central plane. lt will of course be understood that when using -a light source extending laterally somewhat away from the central point 39 or when diS- placing the focus of the cylindrical lens or the parabolic end walls somewhat from the directrix 34 all of this light will not be rendered precisely parallel to the central vertical plane, but the tendency will be to deflect all of the rays toward the central vertical plane so as to concentrate the central portion of the beam.

It will be apparent that some light will be reflected from the main reflector 31, in Fig. 8, so as to pass through the openings 37 and 38 without striking either the end reflectors or the cylindrical lens. All such light will flare outwardly and will result in spots of light displaced laterally in both directions from the main central beam. llf this is found to be undesirable for the purpose for which the apparatus is intended to be employed, the cylindrical lens may be modified as shown in Fig. 9. ln this construction the lens 51 is cylindrical throughout the central portion, that is, throughout the portion between the lines 52 and 53, the line focus of this portion preferably being disposed inthe directrix'of the central parabolic element of the main reector. 0n either side of the central portion 51 are portions 54 and 55, these portions being of such width as to close the spaces 37 and 38 shown in Fic. 8. Thus, when employing the cylindricalD lensl of Fig. 9 with the structure shown in Fig. 2'the lens wouldbe dis osed over the forward opening of the re ector ME in the position obtained by moving the lens of Fig. 9 directly to' the left to the lane of the forward edge of the reector and vend walls F, in which position the line focus of the central portion 51 would be coincident with the directrix D of Fig. 2. With the construction shown in Fig. `9 the light which would otherwise pass through the spaces 37 and 38 (Fig. 8) passes through the negative.

ortions 54 and .55 and is deflected ini end reflectors. lt is true that the negative ,portions 54 and 55 will also deflect the parallel rays passing therethrough from the end reflector, such as rays u, fv, and t, in Fig. 2, but these rays pass almost directly through the negative portions so as to be little a'ected and moreover, the portions of these two beams of light which are deflected inwardly will pass through the main central beam and assist in illuminating the regions on either side of the main beam so as to produce a gradual decrease in the intensity of the beam from the center outwardly. The lateral spread of the beam I'nay be varied by increasing or `diminishing the power of the cylindrical lens or by changing the position of the foci of the end reectors F.

The lateral spread is least when the foci of the lens and end reflectors coincide with' the directrix of the reflector, and by shifting the foci forwardly or rearwardly, central` concentration can be diminished, the lateral spread thereby being increased.

lit is to be understood that such terms as horizontal, vertical, upward, downward, etc., are herein employed merely in a relative sense for convenience in referring to relative positions and directions and that they arenot employed in the absolute sense with respect to the earths surface, although in the preferred use of our apparatus they are also accurate with reference to the earths surface.

jWe claim:

1. Light projection apparatus comprising a substantially parabolic cylindrical reflector, and light deflectin means having a focussubstantially in t e directriX of the [central parabolic element of the reflector for redirecting a .portion of the light reflected from'the cylindrical reflector.

2. Light projection apparatus comprising a substantially4 parabolic Icylindrical reflector, and light deflecting means having a line focus substantially coincident with the directrix of the central parabolic element of the'reflector for concentrating the projected light` in the region of the plane of said central element and directrix. j

3. Light projection apparatus comprising a substantially parabolic cylindrical reflector, and a lens having a focus substantially in the directrix of the central parabolic element of-'the reflector fo redirecting a portion of the light reliecte from the cylindrical reflector.

4. Light projection apparatus comprising a substantially parabolic cylindrical reflector, and a lens having a line focus substantially coincident with the directrix of the central -parabolic element of the reflector for concentrating the light 'reflected from the ref flector along the central plane containing 4said element and directrix.

5. Light projection apparatus comprising a substantially parabollc cylindrical reflector; light diffusing end Walls for the reflector, and a cylindrical lens disposed in `front of the` cylindricalreflector with its `focus substantially in the directrix of the central parabolic 4element ofwthe reflector so as to redirecta portion' of the light reflected from the cylindricalj'reiector at least into approximate parallelismv with the central plane containing vsaid element and directrix.

6. Light projection apparatus com rising a cylindrical reflector. and light de ecting means for redirecting a portion of the light reflected from vthe cylindrical reflector, the light decting means having a line' focus disposed at -the rear of the reflector in a plane substantially perpendicular to the axis of the cylindricalv reflector. h

7. Light projection apparatus comprising a substantially v arabolic cylindrical reliec# torand a cylin rical lens disposedin front ofthe reflector with its focus disposed at the rear of the reieetor in a plane substantially perpendicular to the axis of the cylindricall j reflector. Y

8. Light projectionapparatus comprisin a substantially cylindrical rellectorand en reflecting members, lthe vertical elements of the end reflecting members being substantially str-aight and the horizontal elements of the end members being conic sections.

9. Light projection apparatus comprisingv a substantially parabolic cylindrical reflector, the straight elements of which are disposed horizontally or controlling the vertical spread of the beam, and refracting means having straight vertical elements, said re fracting means being designed to control the toward the sides.

11. Light projection apparatus `comprising acylindricalreiiector having a horlzontal focal region, end reflectors for the cylindrical reflector, the end reflectors havin foci at the rearsofY the main-reflector, and refracting means forwardly of said ocal region for controlling the horizontal spread of the project-ed beam. f

A'12. Light projection apparatus compris-v ing a cylindrical reflector having a horizontal focal region, end reflectors disposed to deflect a portionfof the light reflected from the cylindrical reflector in such manner as to control the horizontal spread of the beam, 'and refracting vmeans for refracting another portion of the light reiiected from-the cylindrical reflector so as also to control the horizontal spread of the beam.

Signed by usv at Boston, Massachusetts',

` this 8th day of May, 1917.

lotivrli Eintr coNKLiN. HERBERT rnncivat notament. 

